The father of a 13-year-old girl who may be Lindsay Lohan's half-sister said the family went public with the story after Lohan's father, Michael, repeatedly refused to provide support.

The Montana girl's family is looking into legal options to pursue once they establish that Michael Lohan is the father, Daryl Kaufmann said in a phone interview. He said his wife, Kristi Kaufmann, had been trying to get Michael Lohan to support their daughter for years.

"She had enough," Kaufmann said of his wife when reached by telephone at their home in Florence, Mont. "She just wanted it exposed. So he's going to end up having to do something."

Michael Lohan told reporters Friday he learned of Kristi Kaufmann's claim after receiving letters and photos from her while incarcerated on drunk driving charges. Lohan acknowledged having a sexual relationship with Kaufmann while he was separated from wife Dina Lohan 13 years ago.

"Why would someone without taking a test put something out there like this?" Lohan said. "What if it's negative? What is that going to do to her own child and my children? Is this for the fame? There was correspondence where she said Ashley, her daughter, wants to be an actress, and she's so talented."

OK! magazine first reported Kaufmann's claim Friday. Daryl Kaufmann said his wife called and e-mailed several magazines in an attempt to expose Lohan as the father of her daughter. Kaufmann said OK! was the only publication to respond to her messages and did not pay for the story or photos of Ashley.

"She used OK! magazine to get the ball rolling," he said.

Michael Lohan acknowledged on Friday there was a resemblance in the photos of Ashley to his daughters. He said he recently received a "senseless, ridiculous voicemail" from Kristi Kaufmann, whose maiden name is Horn. He said he has taken a paternity test and will take responsibility for the child if he is proved to be the biological father. It was not clear when the results would come back.

Lindsay Lohan's publicist, Leslie Sloane Zelnick, did not return messages left by the AP. Michael Lohan's publicist, Leslie Kellner Taylor, did not return messages seeking additional comment.

Michael Lohan, a former Wall Street broker, settled a long-simmering divorce with Dina Lohan last August, though they returned to court in Long Island last month over custody issues. The pair married in 1985. He was released from prison in March 2007 after serving nearly two years for attempted assault and driving while intoxicated.

Michael Lohan said he hasn't spoken with Lindsay or any of his other three children — Cody, 12; Ali, 14; Michael, 20 — about Kaufmann's claim. Ali and Cody currently live with their mother in Merrick, N.Y., and are featured on the E! reality show "Living Lohan."

Lindsay Lohan is currently filming a movie titled "Labor Pains."